Sweet Refrigerator Pickles

Combine cucumber slices and salt in a heatproof bowl and set aside for 90 minutes.

Place cucumbers in a sieve and wash well under running cold water. Drain well, return cucumbers to the bowl, and add onion.

Combine white sugar, white wine vinegar, apple cider vinegar, brown sugar, mustard seeds, celery seeds, and turmeric in a saucepan over medium heat. Bring to a boil and stir to dissolve sugar, about 3 minutes. Pour liquid over cucumbers and let stand for 1 hour at room temperature.

Transfer cucumbers and liquid to a container with a tight-fitting lid, cover, and refrigerate for 24 hours.